use base64::Engine;
use base64::engine::general_purpose::STANDARD;

const K: [u8; 16] = [0u8; 16];
const V: [u8; 16] = [1u8; 16];
const BLOCK_SIZE: usize = 4;

pub fn encryption(input: String) -> String {
    let input_bytes= input.as_bytes();
    let padded_data = pkcs7(input_bytes);
    let input_ready_data: Vec<u32> = padded_data.chunks(4)
        .map(|c| u32::from_be_bytes([c[0], c[1], c[2], c[3]]))
        .collect();

    let mut zuc = Zuc::new();
    zuc.init(K, V);
    let ret = zuc.work(input_ready_data);

    let mut bytes = Vec::new();
    for i in ret {
        bytes.extend(i.to_be_bytes());
    }
    STANDARD.encode(bytes)
}

fn pkcs7(input_bytes: &[u8]) -> Vec<u8> {
    let padding_len = BLOCK_SIZE - input_bytes.len() % BLOCK_SIZE;
    let mut padded_data = Vec::from(input_bytes);
    padded_data.extend(vec![padding_len as u8; padding_len]);
    padded_data
}

const S0: [u8; 256] = [
    0x3E, 0x72, 0x5B, 0x47, 0xCA, 0xE0, 0x00, 0x33, 0x04, 0xD1, 0x54, 0x98, 0x09, 0xB9, 0x6D, 0xCB,
    0x7B, 0x1B, 0xF9, 0x32, 0xAF, 0x9D, 0x6A, 0xA5, 0xB8, 0x2D, 0xFC, 0x1D, 0x08, 0x53, 0x03, 0x90,
    0x4D, 0x4E, 0x84, 0x99, 0xE4, 0xCE, 0xD9, 0x91, 0xDD, 0xB6, 0x85, 0x48, 0x8B, 0x29, 0x6E, 0xAC,
    0xCD, 0xC1, 0xF8, 0x1E, 0x73, 0x43, 0x69, 0xC6, 0xB5, 0xBD, 0xFD, 0x39, 0x63, 0x20, 0xD4, 0x38,
    0x76, 0x7D, 0xB2, 0xA7, 0xCF, 0xED, 0x57, 0xC5, 0xF3, 0x2C, 0xBB, 0x14, 0x21, 0x06, 0x55, 0x9B,
    0xE3, 0xEF, 0x5E, 0x31, 0x4F, 0x7F, 0x5A, 0xA4, 0x0D, 0x82, 0x51, 0x49, 0x5F, 0xBA, 0x58, 0x1C,
    0x4A, 0x16, 0xD5, 0x17, 0xA8, 0x92, 0x24, 0x1F, 0x8C, 0xFF, 0xD8, 0xAE, 0x2E, 0x01, 0xD3, 0xAD,
    0x3B, 0x4B, 0xDA, 0x46, 0xEB, 0xC9, 0xDE, 0x9A, 0x8F, 0x87, 0xD7, 0x3A, 0x80, 0x6F, 0x2F, 0xC8,
    0xB1, 0xB4, 0x37, 0xF7, 0x0A, 0x22, 0x13, 0x28, 0x7C, 0xCC, 0x3C, 0x89, 0xC7, 0xC3, 0x96, 0x56,
    0x07, 0xBF, 0x7E, 0xF0, 0x0B, 0x2B, 0x97, 0x52, 0x35, 0x41, 0x79, 0x61, 0xA6, 0x4C, 0x10, 0xFE,
    0xBC, 0x26, 0x95, 0x88, 0x8A, 0xB0, 0xA3, 0xFB, 0xC0, 0x18, 0x94, 0xF2, 0xE1, 0xE5, 0xE9, 0x5D,
    0xD0, 0xDC, 0x11, 0x66, 0x64, 0x5C, 0xEC, 0x59, 0x42, 0x75, 0x12, 0xF5, 0x74, 0x9C, 0xAA, 0x23,
    0x0E, 0x86, 0xAB, 0xBE, 0x2A, 0x02, 0xE7, 0x67, 0xE6, 0x44, 0xA2, 0x6C, 0xC2, 0x93, 0x9F, 0xF1,
    0xF6, 0xFA, 0x36, 0xD2, 0x50, 0x68, 0x9E, 0x62, 0x71, 0x15, 0x3D, 0xD6, 0x40, 0xC4, 0xE2, 0x0F,
    0x8E, 0x83, 0x77, 0x6B, 0x25, 0x05, 0x3F, 0x0C, 0x30, 0xEA, 0x70, 0xB7, 0xA1, 0xE8, 0xA9, 0x65,
    0x8D, 0x27, 0x1A, 0xDB, 0x81, 0xB3, 0xA0, 0xF4, 0x45, 0x7A, 0x19, 0xDF, 0xEE, 0x78, 0x34, 0x60
];

const S1: [u8; 256] = [
    0x55, 0xC2, 0x63, 0x71, 0x3B, 0xC8, 0x47, 0x86, 0x9F, 0x3C, 0xDA, 0x5B, 0x29, 0xAA, 0xFD, 0x77,
    0x8C, 0xC5, 0x94, 0x0C, 0xA6, 0x1A, 0x13, 0x00, 0xE3, 0xA8, 0x16, 0x72, 0x40, 0xF9, 0xF8, 0x42,
    0x44, 0x26, 0x68, 0x96, 0x81, 0xD9, 0x45, 0x3E, 0x10, 0x76, 0xC6, 0xA7, 0x8B, 0x39, 0x43, 0xE1,
    0x3A, 0xB5, 0x56, 0x2A, 0xC0, 0x6D, 0xB3, 0x05, 0x22, 0x66, 0xBF, 0xDC, 0x0B, 0xFA, 0x62, 0x48,
    0xDD, 0x20, 0x11, 0x06, 0x36, 0xC9, 0xC1, 0xCF, 0xF6, 0x27, 0x52, 0xBB, 0x69, 0xF5, 0xD4, 0x87,
    0x7F, 0x84, 0x4C, 0xD2, 0x9C, 0x57, 0xA4, 0xBC, 0x4F, 0x9A, 0xDF, 0xFE, 0xD6, 0x8D, 0x7A, 0xEB,
    0x2B, 0x53, 0xD8, 0x5C, 0xA1, 0x14, 0x17, 0xFB, 0x23, 0xD5, 0x7D, 0x30, 0x67, 0x73, 0x08, 0x09,
    0xEE, 0xB7, 0x70, 0x3F, 0x61, 0xB2, 0x19, 0x8E, 0x4E, 0xE5, 0x4B, 0x93, 0x8F, 0x5D, 0xDB, 0xA9,
    0xAD, 0xF1, 0xAE, 0x2E, 0xCB, 0x0D, 0xFC, 0xF4, 0x2D, 0x46, 0x6E, 0x1D, 0x97, 0xE8, 0xD1, 0xE9,
    0x4D, 0x37, 0xA5, 0x75, 0x5E, 0x83, 0x9E, 0xAB, 0x82, 0x9D, 0xB9, 0x1C, 0xE0, 0xCD, 0x49, 0x89,
    0x01, 0xB6, 0xBD, 0x58, 0x24, 0xA2, 0x5F, 0x38, 0x78, 0x99, 0x15, 0x90, 0x50, 0xB8, 0x95, 0xE4,
    0xD0, 0x91, 0xC7, 0xCE, 0xED, 0x0F, 0xB4, 0x6F, 0xA0, 0xCC, 0xF0, 0x02, 0x4A, 0x79, 0xC3, 0xDE,
    0xA3, 0xEF, 0xEA, 0x51, 0xE6, 0x6B, 0x18, 0xEC, 0x1B, 0x2C, 0x80, 0xF7, 0x74, 0xE7, 0xFF, 0x21,
    0x5A, 0x6A, 0x54, 0x1E, 0x41, 0x31, 0x92, 0x35, 0xC4, 0x33, 0x07, 0x0A, 0xBA, 0x7E, 0x0E, 0x34,
    0x88, 0xB1, 0x98, 0x7C, 0xF3, 0x3D, 0x60, 0x6C, 0x7B, 0xCA, 0xD3, 0x1F, 0x32, 0x65, 0x04, 0x28,
    0x64, 0xBE, 0x85, 0x9B, 0x2F, 0x59, 0x8A, 0xD7, 0xB0, 0x25, 0xAC, 0xAF, 0x12, 0x03, 0xE2, 0xF2
];

const D: [u16; 16] = [
    0x44D7, 0x26BC, 0x626B, 0x135E, 0x5789, 0x35E2, 0x7135, 0x09AF,
    0x4D78, 0x2F13, 0x6BC4, 0x1AF1, 0x5E26, 0x3C4D, 0x789A, 0x47AC
];

pub struct Zuc {
    r: [u32; 2],
    x: [u32; 4],
    lfsr: Vec<u32>,
}

impl Zuc {
    pub fn new() -> Self {
        Self {
            r: [0; 2],
            x: [0; 4],
            lfsr: vec![0u32; 16],
        }
    }

    pub fn init(&mut self, key: [u8; 16], iv: [u8; 16]) {
        for i in 0..16 {
            self.lfsr[i] = make_uint31(key[i], D[i], iv[i]);
        }
        for _ in 0..32 {
            self.bit_reorganization();
            let w = self.f();
            self.lfsr_init(w >> 1)
        }
    }

    pub fn work(&mut self, input: Vec<u32>) -> Vec<u32> {
        let mut ret = vec![];
        let len = input.len();
        let key_stream = self.generate_key_stream(len);
        for i in 0..len {
            ret.push(input[i] ^ key_stream[i]);
        }
        ret
    }

    fn bit_reorganization(&mut self) {
        self.x[0] = (self.lfsr[15] & 0x7fff8000) << 1 | (self.lfsr[14] & 0xffff);
        self.x[1] = (self.lfsr[11] & 0xffff) << 16 | (self.lfsr[9] >> 15);
        self.x[2] = (self.lfsr[7] & 0xffff) << 16 | (self.lfsr[5] >> 15);
        self.x[3] = (self.lfsr[2] & 0xffff) << 16 | (self.lfsr[0] >> 15);
    }

    fn f(&mut self) -> u32 {
        let w = ((((self.x[0] ^ self.r[0]) as u64) + self.r[1] as u64) & 0xffffffff) as u32;
        let w1 = ((self.r[0] as u64 + self.x[1] as u64) & 0xffffffff) as u32;
        let w2 = self.r[1] ^ self.x[2];
        let u = l1(((w1 & 0x0000ffff) << 16) | (w2 >> 16));
        let v = l2(((w2 & 0x0000ffff) << 16) | (w1 >> 16));
        let u0 = u >> 24;
        let u1 = (u >> 16) & 0xff;
        let u2 = (u >> 8) & 0xff;
        let u3 = u & 0xFF;
        let v0 = v >> 24;
        let v1 = (v >> 16) & 0xff;
        let v2 = (v >> 8) & 0xff;
        let v3 = v & 0xFF;
        self.r = [make_uint32(S0[u0 as usize], S1[u1 as usize],
                              S0[u2 as usize], S1[u3 as usize]),
            make_uint32(S0[v0 as usize], S1[v1 as usize],
                        S0[v2 as usize], S1[v3 as usize])];
        w
    }

    fn lfsr_init(&mut self, u: u32) {
        let s16 = addition_uint31(self.lfsr_next(), u);
        self.lfsr.push(s16);
        if self.lfsr.len() > 16 {
            self.lfsr.remove(0);
        }
    }

    fn lfsr_work(&mut self) {
        let s16 = self.lfsr_next();
        self.lfsr.push(s16);
        if self.lfsr.len() > 16 {
            self.lfsr.remove(0);
        }
    }

    fn lfsr_next(&self) -> u32 {
        let f = self.lfsr[0];
        let v = rotl_uint31(self.lfsr[0], 8);
        let f = addition_uint31(f, v);
        let v = rotl_uint31(self.lfsr[4], 20);
        let f = addition_uint31(f, v);
        let v = rotl_uint31(self.lfsr[10], 21);
        let f = addition_uint31(f, v);
        let v = rotl_uint31(self.lfsr[13], 17);
        let f = addition_uint31(f, v);
        let v = rotl_uint31(self.lfsr[15], 15);
        let f = addition_uint31(f, v);
        f
    }

    fn generate_key_stream(&mut self, len: usize) -> Vec<u32> {
        let mut key_stream_buffer = vec![];
        self.bit_reorganization();
        self.f();
        self.lfsr_work();
        for _ in 0..len {
            self.bit_reorganization();
            let z = self.f() ^ self.x[3];
            key_stream_buffer.push(z);
            self.lfsr_work();
        }
        key_stream_buffer
    }
}

fn addition_uint31(a: u32, b: u32) -> u32 {
    let c = a + b;
    (c & 0x7fffffff) + (c >> 31)
}

fn make_uint31(a: u8, b: u16, c: u8) -> u32 {
    ((a as u32) << 23) & 0x7fffffff | ((b as u32) << 8) & 0x7fffffff | (c as u32)
}

fn make_uint32(a: u8, b: u8, c: u8, d: u8) -> u32 {
    (((a as u32) << 24) & 0xffffffff) | (((b as u32) << 16) & 0xffffffff) | (((c as u32) << 8) & 0xffffffff) | d as u32
}

fn l1(x: u32) -> u32 {
    x ^ rotl_uint32(x, 2) ^ rotl_uint32(x, 10) ^ rotl_uint32(x, 18) ^ rotl_uint32(x, 24)
}

fn l2(x: u32) -> u32 {
    x ^ rotl_uint32(x, 8) ^ rotl_uint32(x, 14) ^ rotl_uint32(x, 22) ^ rotl_uint32(x, 30)
}

fn rotl_uint32(a: u32, shift: i32) -> u32 {
    ((a << shift) | (a >> (32 - shift))) & 0xffffffff
}

fn rotl_uint31(a: u32, shift: i32) -> u32 {
    ((a << shift) | (a >> (31 - shift))) & 0x7fffffff
}